An important function of the brain is to scan incoming sensory information for the presence of biologically relevant features and process and act on this information. For humans, the most salient signals of emotion are often social in nature, such as expressions of fear or anger. The goal of the current competing renewal is to study the nature and neural architecture of emotion processing across the first three years of life. Five-, seven-, and twelve-month-old infants, as well as three-year-old typically developing children will serve as participants across 5 specific aims. Aim 1 seeks to examine the neural and cardiac correlates of the infant's ability to process emotion in both faces and non-face stimuli. Aim 2 examines a similar question, except that autonomic activity (skin conductance and pupil diameter) will be recorded in conjunction with functional Near Infrared Spectroscopy (fNIRS). Aim 3 seeks to elucidate the neural networks involved in emotion processing, and will do so by using state-of-the-art signal processing software to extract theta activity from the ongoing EEG. Aim 4 will focus on individual differences in emotion processing viewed through the lens of genetics; specifically, all infants serving as participants in Aims 1 and 2 will be genotyped, with most attention focused on 5 SNPs, with an additional 5 SNPs serving as a secondary aim. All SNPS have been shown to be relevant to emotion processing in both humans and non-human species. Finally, in Aim 5 we examine whether early biases in emotion processing (i.e., whether infants show greater visual or neural activity to one emotion vs. another; e.g., fear) predict (or are associated with) behavioral inhibition and anxiety. Although the current project focuses on typically developing children, this work has enormous implications for children and adults who suffer from deficits in social-emotional communication. First, this work seeks to explicate the ontogeny of facial emotion processing; an ability that likely provides a foundation upon which higher-level social communication builds. As a result, it may well be the case that errors in this ability that occur early in development can develop into more insidious deficits that occur later i development. Second, the approach adopted in this project is highly innovative, and can easily be extended to various clinical populations, such as toddlers with autism or children diagnosed with depression or bipolar illness.